What they showed at Numrich, which was all I had to go by, and from The Encyclopedia of Modern Firearms, the 235 is the only parts list with drawing I can find, but Numrich shows the same release spring used in both the 235 and 33, or 33A. It is a straight wire spring, but mid ways, it has a slight V shape in it, then has a one turn loop on it. That's why I thought they were similar. It is one of the only parts that they show a photo of for a 33. The 235's have two other wire springs, one, a rather complicated sear spring, and next, a semi-straight cartridge stop spring. The rest are all coil springs.
The 33 does have the same reciprocating magazine tube as the 235 doesn't it, or it is attached to the bolt? I looked at a photo of a 33, and it looked like it did. That's about as far as I can go with it, as I don't have anything on the 33.
Update:
I ran across this for a 33A. The catalog page looks like the same they showed in the Brownell's Encyclopedia for a 235. Though this isn't a 33, but a 33A.
Noble 33A by
matneyw, on Flickr